Usually, the protection for the communication network service is realized by using alternative routes of the same layer in the communication equipment, e.g. automatic protection switch of SDH and ATM (reference to ITU-T G.841 and I.630). Such protection is characterized with providing two passages (SDH channels or ATM VPC/VCC) on the same layer of communication equipment, namely working passage and protecting passage. Commonly, working passage transmits service, when there are some problems with working passage, protecting passage will transmit service, and the switch between working passage and protecting passage is realized by the node adjacent to the malfunction position or the node influenced by malfunction. However, there need many nodes involved to realize protection step, even need some relevant nodes coordinate, therefore, it is complicated to realize, thus influence its efficiency and stability.
In the MSPP, ATM traffic are provided by ATM processing module which has the following main functions: to drop ATM traffic from other nodes of sub-network to said node; to add ATM traffic from said node to other nodes on sub-network. As a matter of fact, the ATM traffic processing module of certain node doesn't process the ATM traffic between other nodes of sub-network. As a function module, ATM processing module only lose its function of adding and dropping the ATM traffic, instead of influencing service between other nodes. There are some similar problems in other multi-layer network equipment. Therefore, if traditional ATM traffic protection method is adopted, the ATM processing module and SDH processing module in MSPP are treated as two independent devices, which result in failure of making full use of the advantage of combination of each other.